1. Field of the Invention
The present invention relates to a semiconductor device. In particular, the present invention relates to a logic integrated memory device in which a logic circuit and a memory are mounted on a single chip. More specifically, the present invention relates to generation of internal power to be supplied to a logic integrated memory device.
2. Description of the Background Art
Recent advancement of a semiconductor fabrication technique makes it possible to realize a logic integrated memory device in which a logic circuit and a memory capable of accessing data in the logic circuit are mounted on a single chip. This logic integrated memory device can enhance a transfer rate between the logic circuit and the memory and, therefore, makes it possible to realize processing at a higher speed. In addition, this logic integrated memory device can be reduced in size and, therefore, is positively applied to a portable telephone and the like.
As described above, the logic integrated memory device is applied to a portable telephone and, therefore, must be stably operated even when a battery with a relatively large variation in voltage is used as an external power supply. For this reason, a general logic integrated memory device includes an internal power generation circuit supplied with external power to generate stable internal power with a small variation in voltage. The internal power generation circuit generates internal power based on a reference voltage generated by a reference voltage generation circuit.
Therefore, the reference voltage generation circuit is configured to generate a reference voltage with a small variation with respect to various stationary disturbances and dynamic disturbances such as a variation in voltage of external power, a variation in process, a change in ambient temperature, and an intrusion of noise. For example, Japanese Patent Laying-Open Publication No. 2004-318235 discloses a reference voltage generation circuit capable of changing temperature dependence of a reference voltage from a predetermined positive temperature characteristic to a predetermined negative temperature characteristic in order to prevent internal power from being varied due to a change in ambient temperature.
On the other hand, a logic integrated memory device to be applied to a portable telephone or the like must suppress its power consumption to reduce a consumption amount of power in a battery and to prolong an operation time. In order to reduce conversion loss in an internal power generation circuit, therefore, such a logic integrated memory device may be directly driven with an external power supply (a battery).
However, if the logic integrated memory device is directly driven with an external power supply, a variation in voltage becomes large. Consequently, there arises a problem that a stable operation can not be ensured. Accordingly, it is difficult to realize a configuration capable of achieving both a stable operation and lower power consumption.